Paper having high wet strength and process of producing the same



Patented July 28, 1942 PAPER HAVING HIGH WET STRENGTH AND PROCESS OF PRODUCING THE SAME Raymond P. Hoilerbert, Stamford, Conn., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine,

No Drawing. Original application February 6,

1940, Serial No. 317,527. Divided and this application February 6, 1940, Serial No. 317,526

2 Claims.

This invention relates to the production of paper having a high wet strength and improved chemical resistance.

An object of this inventionis to produce paper I having a high wet strength. Another object of Example Parts Melamine 78 A solution of isopropanol in water"- 53 Formalin (37% formaldehyde in water)--- 100 A 10% solution of triethanoline in water 2.2

These substances are mixed and reacted at about 55-60 C. for 1-2 hours. During the reaction the pH is preferably maintained at about 7.0. The temperature may then be raised to about C. for 20 minutes and then to about C.

for 20-30 minutes or until a clear syrup has been formed. This syrup is water-soluble and may be cooled to room temperature.

About 16 parts of the syrup prepared above are mixed with 184 parts of water and 11 parts of an accelerator solution containing 1.75% of a mixture consisting of 4 parts of hexamethylene tetramine and 30 parts of diammonium phosphate. This composition is applied to a paper sheet in any convenient manner as for example by the use of rolls, one of which dips into the treating solution, by spraying, etc. The treated paper is preferably passed through a set of squeeze rolls to remove the excess treating solution and to effect good impregnation of the paper. The resin content of the paper is thus adjusted to between 0.5 and 5%. The paper may be dried in an oven or other suitable apparatus at about C., about 10 minutes being required for this operation. The dried impregnated paper is then cured at about 150 C. for approximately 3 minutes. The resulting treated paper has very high wet strength and good chemical resistance thereby rendering it suitable for various uses wherein these properties are particularly desirable.

Optionally the treated paper may be dried 55 tion has a wide variety of uses, e. g., as filter and cured simultaneously but it has been found that somewhat superior results are obtained if the paper be dried at around 100 C. and then the curing of. the resin effected at about C.

To obtain optimum properties only a small proportion of resin based on the weight of the dry paper should be applied, i. e., from about 0.5% to 5%.- Larger proportions of resin render the paper unsuitable for most purposes.

Other materials may be mixed with or emulsified with the melamine-formaldehyde resin syrup in order to desirably modify the properties which are obtained with the melamineformaldehyde resin alone. Examples of these are casein, rosin, albumen, alkyd resins, ureaformaldehyde resins, phenol-formaldehyde resins, etc. It is to be noted, however, that in order to obtain the desirable properties which result from the use of melamine-formaldehyde resins,

it is necessary to utilize a substantial proportion of the melamine-formaldehyde condensation products, e. g., above about 25% of the total resin present should be melamine-formaldehyde condensation product.

In order to obtain good impregnation of the paper with the resinous syrup containing melamine-formaldehyde condensation products, suitable wetting agents may be incorporated such as for example sodium lauryl sulphate, sodium lauryl sulphonate, the soluble salts of the esters of sulphosuccinic acid (e. g., the sodium salt of the dioctyl ester of sulphosuccinic acid), the sodium salt of alkylated naphthalene sulphonic acids, ordinary soaps, etc. Suitable surface tension modifiers may also be incorporated in the impregnating solutions, e. g., ethanol, acetone, etc.

Obviously other catalysts may be used in place of the one described in the above example or the melamine-formaldehyde condensation product may be polymerized without the use of any catalyst. Examples of other suitable catalysts are: phosphoric acid, phthalic acid, the ammonium or amine salts of such acids, alum, ammonium chloride, etc. These may either be added to the resin treating solution or they may be applied to the paper after impregnation with the resinous syrup. I

Higher or lower ratios of formaldehyde to melamine than that in the above example may be used, e. g., from about 1:1 up to 6:1 or even higher, although ratios between 2:1 and 4:1 are preferred.

Paper treated in accordance with my invenpaper for laminating, as wrapping material ior damp articles such as meat, etc. Furthermore paper treated with melamine-formaldehyde condensation products as described herein is also suitable for paper towels, toilet tissues, etc.

This application is a division of my co-pending application Serial No. 317,527, filed February 6, 1940, and entitled Method of producing paper having high wet strength and products thereo Obviously many modifications and variations in the processes and products described herein may be made without departing from the spirit and scope or the invention as defined in the appended claims.

I claim: 1. A process of increasing the wet strength or paper which comprises treating paper with an aqueous solution or a melamine-formaldehyde condensation product. adjusting the melamineformaldehyde condensation product content so that the proportion of the condensation product is about (LS-5% oi the weight of the paper (dry basis) and polymerizing said condensation product.

2. Paper impregnated with about 0.5-5% oi the weight of the paper (dry basis) of a melamine-ioraldehyde resin, said paper having a higher wet strength than the same paper which has not been impregnated with resin.

RAYMOND P. HOFFERBERT.

CERTIFICATE OF CORRECTION.

Patent No. 2,291,079. July 28, 1914.2.

RAYMOND P HOFFERBERT It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Rage 1, first column, line 214., for 'triethanoline" read -triethano1amine--; and that the said.LetteI's Patent should be read with this correction therein that the seme may conform to the record .of the case in the Patent Office.

Signed and sealed this 27th day of October, A. D. 19142.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

